1. Field of the Invention
This invention relates to a method and apparatus for bone size gauging and, more particularly, to the utilization of a hemispherical member with a pressure responsive exterior surface capable of changing characteristics, color or shape, when contacted by a surface into which it is inserted.
2. Description of the Background Art
It is common for orthopedic surgeons to use a testing device or gauge for determining the proper size of prosthetic implant for a socket joint when replacing a patient's natural ball joint. The most common technique involves the surgeon making an initial estimate of the artifical ball to be utilized based upon the patient's x-rays when viewed with overlays and templates. The surgeon will then have available a plurality of test balls of different sizes which might fit properly. During the operation, after the bone-receiving socket has been cleaned, the surgeon will then insert one test ball into the socket and effect a limited degree of rotation or testing movement to feel the fit. Thereafter, the surgeon will then try another ball of a slightly different size. Based on the feel that the surgeon receives from such insertions and testing movements, he would use his judgement and experience to determine the proper ball size to be utilized for the particular socket.
During such procedures, it is only the experience of the surgeon, who has performed such tests before, that can be relied upon for the selection of the proper size ball for a successful implant operation. As such, the practice is limited to use by experienced surgeons and requires extended time to insert, move and determine the proper ball size from a plurality of closely sized balls.
The shortcomings of known methods and apparatus for use by surgeons in determining the proper ball size are evidenced by the large number of patents issued on devices attempting to overcome the deficiencies in the prior art. By way of example, note U.S. Pat. Nos. 2,737,724 to Herz; 4,135,517 to Reale; 4,436,684 to Light; 4,559,936 to Hill: 4,632,111 to Roche; and 4,645,503 to Lin. Each of these patents relates to a method or apparatus for orthopedic bone replacement or the like wherein sizing is a consideration. Note in particular, U.S. Pat. No. 4,517,969 to Halcomb. According to that disclosure, a translucent hemispherical gauge is inserted in a bone socket to be sized. The translucence of the exterior surface, when contacting an area of the bone socket, will indicate the area of contact when viewed by the physician through the contact surface. Viewing the area of contact during the operation with the contact device in place is not always convenient and does not always yield the most efficient results for proper size determination.
As illustrated by the background art, efforts are continuously being made in an attempt to improve bone size gauging. No prior effort, however, provides the benefit attendant with the present invention. Additionally, the prior patents and commercial techniques do not suggest the present inventive combination of component elements arranged and configured as disclosed and claimed herein.
The present invention achieves its intended purposes, objects, and advantages through a new, useful and unobvious combination of component elements, with the use of a minimum number of functioning parts, at a reasonable cost to manufacture, and by employing only readily available materials.
Therefore, it is an object of this invention to provide an improved bone size testing method and apparatus comprising a hemispherical member having a pole on its axis at the distal end and having a bore on its axis at its proximal end; a handle releasably attached to the bore of the hemispherical member; and a pressure responsive surface on the hemispherical member for changing characteristics when brought in contact with a bone socket to be gauged.
It is a further object of the present invention to utilize the area of contact between a hemispherical test device and the bone socket receiving the ball joint in order to effect a readable variation on the surface of the device as effected by the contact.
It is a further object of this invention to change the characteristics, color or shape, of the exterior surface of a hemispherical gauge while in a bone socket sized and to interpret the changes as an indication of the fit between the socket and the gauge.
It is a further object of the present to sequentially insert a plurality of different sized hemispherical gauges into an essentially hemispherical socket in order to determine the best size fit of a ball for the socket.
The foregoing has outlined some of the more pertinent objects of this invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the present invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.